Any half decent video store will have it in the "Classics" or Sci-Fi section.

Over the last few years the quality of what Holywood is churning out is pretty bad. Special effects, once the thing of much money and time, can be generated on a PC of no more power than I'm typing on right now. So the plot can be stolen from a good film or book, rewritten to remove any need for cerebral involvement from the audience (War of the Worlds remake, Planet of the Apes remake, I am Legend (remake of Omega Man which admittedly was a remake of the Vincent Price 1964 film etc etc etc)).

With cheaply available special effects the originals seem pale by comparison, but they had to rely on plot and structure for their effect, something lost on new audiences. It was the Planet of the Apes remake that heralded the remake frenzy of old Sci-Fi, and with what we've seen over the last few years, I hold little hope for the new Day the earth Stood Still.